WO2024138360A1

WO2024138360A1 - Arrangements of radiation detectors in an image sensor

Info

Publication number: WO2024138360A1
Application number: PCT/CN2022/142292
Authority: WO
Inventors: Peiyan CAO; Yurun LIU
Original assignee: Shenzhen Xpectvision Technology Co., Ltd.
Priority date: 2022-12-27
Filing date: 2022-12-27
Publication date: 2024-07-04

Abstract

Disclosed herein is an image sensor. The image sensor has M active areas, with M being a positive integer. The M active areas respectively have M orthogonal projections on a same reference plane. The M orthogonal projections together constitute a completely filled area on the reference plane. The M orthogonal projections are arranged in rows (i), i=1, …, N, with N being an integer greater than 1. For each row of the rows (i), i=1, …, N, there is no overlapping between any two orthogonal projections of that row.

Description

ARRANGEMENTS OF RADIATION DETECTORS IN AN IMAGE SENSOR

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 an image sensor, comprising M active areas, with M being a positive integer. The M active areas respectively have M orthogonal projections on a same reference plane. The M orthogonal projections together constitute a completely filled area on the reference plane. The M orthogonal projections are arranged in rows (i) , i=1, …, N, with N being an integer greater than 1. For each row of the rows (i) , i=1, …, N, there is no overlapping between any two orthogonal projections of said each row.

In an aspect, the M orthogonal projections are respectively M identical squares.

In an aspect, the M identical squares have a same orientation.

In an aspect, the rows (i) , i=1, …, N are identical.

In an aspect, the rows (i) , i=1, …, N have a same orientation.

In an aspect, the M orthogonal projections are respectively M identical squares; a Cartesian coordinate system including an Ox axis and an Oy axis is on the reference plane; the row (p) is offset from the row (p+1) by r+β+Bias in a direction of the Ox axis and by r-α in a direction of the Oy axis, with p being an odd integer and 1≤p≤ (N-1) ; the row (q) is offset from the row (q+2) by 2r-2α in a direction of the Oy axis, with q being an integer and 1≤q≤ (N-2) ; 2r is a length of a diagonal of one of the M identical squares; the smallest distance between any two points respectively of any two adjacent orthogonal projections of any row of the rows (i) , i=1, …, N is equal to 2β; α≥β and (β-α) <Bias< (α-β) .

In an aspect, Bias=0.

In an aspect, β=0.

In an aspect, α is no more than 10%of r.

In an aspect, each square of the M identical squares has a diagonal parallel to the Ox axis.

In an aspect, the reference plane is parallel to a best-fit plane of all sensing elements of the M active areas.

In an aspect, for each row of the rows (i) , i=1, …, N, the active areas of the M active areas corresponding to said each row are coplanar.

In an aspect, for each row of the rows (i) , i=1, …, N, centroids of the active areas of the M active areas corresponding to said each row are collinear.

In an aspect, for each row of the rows (i) , i=1, …, N, centroids of the active areas of the M active areas corresponding to said each row are coplanar.

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 a radiation detector package including the radiation detector and a printed circuit board (PCB) , according to an embodiment.

Fig. 6 schematically shows a cross-sectional view of an image sensor including the packages of Fig. 5 mounted to a system PCB (printed circuit board) , according to an embodiment.

Fig. 7 schematically shows a perspective view of an image sensor, according to an embodiment.

Fig. 8 shows the orthogonal projections of the active areas of the image sensor of Fig. 7 on a reference plane, 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. 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 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 and 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 PACKAGE

Fig. 5 schematically shows a top view of a radiation detector package 500 including the radiation detector 100 and a printed circuit board (PCB) 510. The term “PCB” as used herein is not limited to a particular material. For example, a PCB may include a semiconductor. The radiation detector 100 may be mounted to the PCB 510. The wiring between the radiation detector 100 and the PCB 510 is not shown for the sake of clarity. The package 500 may have one or more radiation detectors 100. The PCB 510 may include an input/output (I/O) area 512 not covered by the radiation detector 100 (e.g., for accommodating bonding wires 514) . The radiation detector 100 may have an active area 190 which is where the pixels 150 (Fig. 1) are located. The radiation detector 100 may have a perimeter zone 195 near the edges of the radiation detector 100. The perimeter zone 195 has no pixels 150, and the radiation detector 100 does not detect particles of radiation incident on the perimeter zone 195.

IMAGE SENSOR

Fig. 6 schematically shows a cross-sectional view of an image sensor 600, according to an embodiment. The image sensor 600 may include one or more radiation detector packages 500 of Fig. 5 mounted to a system PCB 650. The electrical connection between the PCBs 510 and the system PCB 650 may be made by bonding wires 514. In order to accommodate the bonding wires 514 on the PCB 510, the PCB 510 may have the I/O area 512 not covered by the radiation detectors 100. In order to accommodate the bonding wires 514 on the system PCB 650, the packages 500 may have gaps in between. The gaps may be approximately 1 mm or more. Particles of radiation incident on the perimeter zones 195, on the I/O area 512, or on the gaps cannot be detected by the packages 500 on the system PCB 650. A dead zone of a radiation detector (e.g., the radiation detector 100) is the area of the radiation-receiving surface of the radiation detector, on which incident particles of radiation cannot be detected by the radiation detector. A dead zone of a package (e.g., package 500) is the area of the radiation-receiving surface of the package, on which incident particles of radiation cannot be detected by the radiation detector or detectors in the package. In this example shown in Fig. 5 and Fig. 6, the dead zone of the package 500 includes the perimeter zones 195 and the I/O area 512. A dead zone (e.g., 688) of an image sensor (e.g., image sensor 600) with a group of packages (e.g., packages 500 mounted on the same PCB and arranged in the same layer or in different layers) includes the combination of the dead zones of the packages in the group and the gaps between the packages.

In an embodiment, the radiation detector 100 (Fig. 1) operating by itself may be considered an image sensor. In an embodiment, the package 500 (Fig. 5) operating by itself may be considered an image sensor.

The image sensor 600 including the radiation detectors 100 may have the dead zone 688 among the active areas 190 of the radiation detectors 100. However, the image sensor 600 may capture multiple partial images of an object or scene (not shown) one by one, and then these captured partial images may be stitched to form a stitched image of the entire object or scene.

The term “image” in the present patent application (including the claims) is not limited to spatial distribution of a property of a radiation (such as intensity) . For example, the term “image” may also include the spatial distribution of density of a substance or element.

ARRANGEMENT OF ACTIVE AREAS IN AN IMAGE SENSOR

Fig. 7 schematically shows a perspective view of an image sensor 700, according to an embodiment. In an embodiment, the image sensor 700 may be similar to the image sensor 600 of Fig. 6 in terms of structure and function. For example, the image sensor 700 may include 15 radiation detectors 100 (not shown) arranged in 5 rows with each row having 3 radiation detectors 100.

In an embodiment, the 15 radiation detectors 100 of the image sensor 700 may respectively include 15 active areas 190 (not shown) which may respectively have 15 orthogonal projections (not shown in Fig. 7, but shown as 15 orthogonal projections 810 in Fig. 8) on a reference plane 710. In an embodiment, the reference plane 710 may be parallel to a best-fit plane (not shown) of all sensing elements 150 of the 15 active areas 190 of the 15 radiation detectors 100 of the image sensor 700.

Fig. 8 shows the 15 orthogonal projections 810 of the 15 active areas 190 of the 15 radiation detectors 100 of the image sensor 700 (Fig. 7) on the reference plane 710, according to an embodiment. In an embodiment, with reference to Fig. 7 and Fig. 8, the 15 radiation detectors 100 of the image sensor 700 (Fig. 7) may be arranged such that the 15 orthogonal projections 810 are arranged in 5 rows with each row including 3 orthogonal projections 810 as shown in Fig. 8.

Specifically, for example, row (1) may include the orthogonal projections 810 (1, 1) , 810 (1, 2) , and 810 (1, 3) . Row (2) may include the orthogonal projections 810 (2, 1) , 810 (2, 2) , and 810(2, 3) . Row (3) may include the orthogonal projections 810 (3, 1) , 810 (3, 2) , and 810 (3, 3) . Row (4) may include the orthogonal projections 810 (4, 1) ; 810 (4, 2) ; and 810 (4, 3) . Row (5) may include the orthogonal projections 810 (5, 1) ; 810 (5, 2) ; and 810 (5, 3) . Note that row (2) and row (4) are shaded for easy viewing.

In an embodiment, with reference to Fig. 8, the 15 orthogonal projections 810 may be identical squares (as shown) . In an embodiment, the 15 identical square orthogonal projections 810 may have the same orientation (as shown) . In other words, each of the 15 identical square orthogonal projections 810 has a side which is parallel to the same direction (e.g., the north-east direction) .

In an embodiment, with reference to Fig. 8, rows (1) , (2) , (3) , (4) , and (5) may be identical (as shown) . In other words, the 5 rows are the same in terms of size and shape. In an embodiment, in addition to being identical, rows (1) , (2) , (3) , (4) , and (5) may have the same orientation. For example, all the 5 rows are parallel to the east direction (as shown) .

In an embodiment, with reference to Fig. 8, the 15 orthogonal projections 810 may together constitute a completely filled area on the reference plane 710 (as shown) . In other words, there is no point on the reference plane 710 that is not on any of the 15 orthogonal projections 810 and that is completely surrounded by the 15 orthogonal projections 810.

In an embodiment, with reference to Fig. 8, for each row of the 5 rows (i.e., row (1) -row (5) ) , there may be no overlapping between any two orthogonal projections 810 of said each row (as shown) . For example, there is no overlapping between any two orthogonal projections 810 of row (1) . For another example, there is no overlapping between any two orthogonal projections 810 of row (2) .

With reference to Fig. 8, assume a Cartesian coordinate system including an Ox axis and an Oy axis is on the reference plane 710 (as shown) . In an embodiment, the 15 orthogonal projections 810 may be respectively 15 identical squares. Row (p) may be offset from the row (p+1) by r+β+Bias in the direction of the Ox axis and by r-α in the direction of the Oy axis, with p being an odd integer and 1≤p≤4 and α being a positive number smaller than r. Row (q) is offset from row (q+2) by 2r-2α in the direction of the Oy axis, with q being an integer and 1≤q≤3.2r is the length of a diagonal of one of the 15 identical squares. The smallest distance between any two points respectively of any two adjacent orthogonal projections 810 of any row of the 5 rows is equal to 2β, where α≥β and (β-α) <Bias< (α-β) .

For example, row (1) is offset from the row (2) by r+β+Bias in the direction of the Ox axis and by r-α in the direction of the Oy axis. In other words, the translation of row (1) in the direction of the Ox axis by r+β+Bias and then in the direction of the Oy axis by r-α would move row (1) to the position of row (2) .

For another example, row (1) is offset from row (3) by 2r-2α in the direction of the Oy axis. In other words, the translation of row (1) in the direction of the Oy axis by 2r-2α would move row (1) to the position of row (3) .

Note that Fig. 8 shows the case in which Bias=0. If Bias= (β-α) , then the north-east side of the orthogonal projection 810 (2, 1) would be collinear with the south-west side of the orthogonal projection 810 (1, 2) , and the south-east side of the orthogonal projection 810 (2, 1) would be collinear with the north-west side of the orthogonal projection 810 (3, 2) . If Bias= (α-β) , then the north-west side of the orthogonal projection 810 (2, 1) would be collinear with the south-east side of the orthogonal projection 810 (1, 1) , and the south-west side of the orthogonal projection 810 (2, 1) would be collinear with the north-east side of the orthogonal projection 810 (3, 1) .

In an embodiment, with reference to Fig. 8, β may be zero. Note that if β=0, then in each row of the 5 rows, adjacent orthogonal projections 810 touch each other. If β=0, just like when β>0, there is still no overlapping between any two orthogonal projections in a given row. In an embodiment, α may be no more than 10%of r.

In an embodiment, with reference to Fig. 8, each of the 15 square orthogonal projections 810 may have a diagonal parallel to the Ox axis (as shown) .

In an embodiment, with reference to Fig. 7 and Fig. 8, for each row of the 5 rows (i.e., rows (1) – (5) ) , the active areas 190 of the 15 active areas 190 corresponding to said each row may be coplanar. For example, the 3 active areas 190 of the image sensor 700 whose orthogonal projections on the reference plane 710 are row (1) are coplanar. Note that multiple active areas 190 are considered coplanar if all the sensing elements 150 of these multiple active areas 190 are coplanar.

In an embodiment, with reference to Fig. 7 and Fig. 8, for each row of the 5 rows (i.e., rows (1) – (5) ) , the centroids of the active areas 190 of the 15 active areas 190 corresponding to said each row may be collinear. For example, the 3 centroids of the 3 active areas 190 of the image sensor 700 whose orthogonal projections on the reference plane 710 are row (1) are collinear.

In an embodiment, with reference to Fig. 7 and Fig. 8, for each row of the 5 rows (i.e., rows (1) – (5) ) , the centroids of the active areas 190 of the 15 active areas 190 corresponding to said each row are coplanar. For example, the 3 centroids of the 3 active areas 190 of the image sensor 700 whose orthogonal projections on the reference plane 710 are row (1) are coplanar.

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

An image sensor, comprising M active areas, with M being a positive integer,

wherein the M active areas respectively have M orthogonal projections on a same reference plane,

wherein the M orthogonal projections together constitute a completely filled area on the reference plane,

wherein the M orthogonal projections are arranged in rows (i) , i=1, …, N, with N being an integer greater than 1, and

wherein for each row of the rows (i) , i=1, …, N, there is no overlapping between any two orthogonal projections of said each row.
The image sensor of claim 1, wherein the M orthogonal projections are respectively M identical squares.
The image sensor of claim 2, wherein the M identical squares have a same orientation.
The image sensor of claim 1, wherein the rows (i) , i=1, …, N are identical.
The image sensor of claim 4, wherein the rows (i) , i=1, …, N have a same orientation.
The image sensor of claim 1,

wherein the M orthogonal projections are respectively M identical squares,

wherein a Cartesian coordinate system including an Ox axis and an Oy axis is on the reference plane,

wherein the row (p) is offset from the row (p+1) by r+β+Bias in a direction of the Ox axis and by r-α in a direction of the Oy axis, with p being an odd integer and 1≤p≤ (N-1) ,

wherein the row (q) is offset from the row (q+2) by 2r-2α in a direction of the Oy axis, with q being an integer and 1≤q≤ (N-2) ,

wherein 2r is a length of a diagonal of one of the M identical squares,

wherein the smallest distance between any two points respectively of any two adjacent orthogonal projections of any row of the rows (i) , i=1, …, N is equal to 2β,

wherein α≥β, and

wherein (β-α) <Bias< (α-β) .
The image sensor of claim 6, wherein Bias=0.
The image sensor of claim 6, wherein β=0.
The image sensor of claim 6, wherein α is no more than 10%of r.
The image sensor of claim 6, wherein each square of the M identical squares has a diagonal parallel to the Ox axis.
The image sensor of claim 1, wherein the reference plane is parallel to a best-fit plane of all sensing elements of the M active areas.
The image sensor of claim 1, wherein for each row of the rows (i) , i=1, …, N, the active areas of the M active areas corresponding to said each row are coplanar.
The image sensor of claim 1, wherein for each row of the rows (i) , i=1, …, N, centroids of the active areas of the M active areas corresponding to said each row are collinear.
The image sensor of claim 1, wherein for each row of the rows (i) , i=1, …, N, centroids of the active areas of the M active areas corresponding to said each row are coplanar.